Pressure switch



Feb.. 5, 1957 F. MCCLELLAN 2,789,593

PRESSURE SWITCH Filed Aug. 10, 1953' 2O I8 I4 se 2o 2s vh "v "3 JNVENTOR.

6e 68 FRANK MCCLELLAN FIGS,

United States Patent O PRESSURE SWITCH Frank McClellan, Detroit, Mich., assigner to Huron Specialty Company, Ann Arbor, Mich., a corporation of Michigan Application August 16, 1953, Serial No. 373,186

2) Claims. (Cl. 20G- 86) The present invention relates to electrical switches and more particularly to pressure-responsive switches.

The present invention is a continuation-in-part of my prior copending application Serial No. 256,567, which has been abandoned.

One object of the present invention is to provide an improved switch which is closed by the application of pressure thereo-n and automatically returns to open position upon release of pressure.

lt is a further object of the present invention to provide a pressure switch characterized by the use of a relatively thick pad or body of compressible and resilient material provided with a plurality of fastening elements formed of electrically conducting material extending completely through the body so as to compress the material thereat and accordingly to locate at least one exposed surface of the fastening element below the plane of the surface of the pad, in conjunction with two conducting layers, such for example as wire mesh, adapted to be in Contact with the two surfaces of the pad of resilient material and at least one of which layers is normally out of contact with the fastening elements but adapted to be pressed into engagement with one or more of the fastening elements upon the application of pressure to the pad.

Another object of the present invention is to provide a switch of the above type incorporated in a vehicle warning signal device and arranged to close a signal circuit whenever the vehicle is occupied by an unauthorized person. The switch may thus be carried by the front seat of the vehicle, for example, and arranged to be closed whenever the seat is occupied, thereby closing an electric circuit to a signal device within the automobile, such as the horn relay. i

As a feature of the invention, a manual switch is provided in series circuit with the pressure-responsive switch and horn relay, said manual switch being located in a concealed position within the vehicle and normally open except when the vehicle is unattended. Accordingly, only when the manual switch is closed is the pressure-responsive switch operative to energize the horn relay when closed.

It is a further feature of the vide a switch of the above type including a relatively hard and stiff sheet material extending over the upper surfacesuch sheet material beingof the switch device proper, suitable to permit the driving of a wheeled vehicle,such as a grocery cart or automobile, over the switch 'for actuation thereof.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings wherein:

- Figure l is a top plan view of a preferred form of pressure-responsive switch with parts broken away in order better to illustrate the details of construction thereof.

Figure 2 is a vertical sectional view of the device shown iu'Figure l.

present invention to pro-V extends beyond the edges of Figure 3 is a diagrammatic View of the pressure-responsive switch incorporated in a vehicle warning signal circuit.

Figure 4 is an enlarged sectional view through a difierent embodiment of the present invention.

Figure 5 is a fragmentary section through a device in which the pressure switch structure is incorporated in an enclosure including at least an upper surface member of relatively hard stiff sheet material.

Figure 6 is a fragmentary section through a device in which the switch structure includes a relatively hard stiff sheet material overlying it, the assembly being enveloped within a sealing enclosure or casing.

Referring more particularly to the drawings and especially to Figures l and 2 thereof, the pressure-responsive switch there shown is generally indicated by the numeral 10 and comprises a llat generally rectangular body or pad 12 of resilient, compressible dielectric material, such as solid rubber, foam rubber, sponge rubber, plastic or the like. Engaging opposite sides of the body 12 are at Sheets 14 of electrically conducting material which may take the form of metallic screens as shown.

Extending through body 12 at a plurality of points are connector elements 16 which may consist of ordinary commercially available staples, having contact parts 18 exposed at opposite surfaces of the body 12. Staples 16 will be formed of metal or other electrically conducting material.

As will be seen in Figure 2, contacts 18 of each staple pinch together or compress the portions 2l) of body 12 through which the respective staples extend, thereby producing dimples, indentations or recesses in which the contac-t portions 18 are located, so that the metal sheets 14 engaging the remaining uncompressed portion of said body, are spaced apart a greater distance than, and therefore out of contact with, the contact parts 18 of each staple.

Electrical leads 22 and 24 are respectively connected to the metal sheets 14 for connection of the switch in a circuit such as the Warning signal circuit illustrated in Figure 3. Enveloping the assembly thus far described is a flexible waterproof enclosure or casing 26 of a dielectric material such as rubber or plastic, having provision of course for the leads 22 and 24 to pass therethrough. As partially shown in Figure 2, the casing 26 may consist of two layers of material secured together at the edges as indicated at 27.

The present invention lends itself admirably to the construction of a vapor-proof switch, since the enclosure or casing 26 may be of vapor-proof flexible material, and any openings therein readily sealed.

In the normal or uncompressed condition of the body 12, the metal sheets 14 are out of contact with the contact parts 18 of the staples, so that the circuit across the sheets and through the staples is ordinarily open. How ever, when suliicient pressure is applied forcing sheets 14 inwardly or toward each other, contact is made by the sheets with the opposite contact parts 18 of the staples closing the circuit therethrough. It will be understood that the circuit is closed even though only one of the staples contacts the two metal sheets. However, by employing a large number'of connector elements or staples, closing of the circuit is practically assured even though the pressure acting to close the switch acts only on a small portion thereof.

It will be noted that the perimeter 13 of the body sheets 14, preventing direct contact of the sheets when pressure is applied thereon. Another method of prevention is to cover the edges of sheets 14 with a suitable non-conducting material such as adhesive tape 15, shown at the upper right corner of Figure 2. This edge binding of the sheets 14 is particularly important where relatively thin bodies are used,

weer@ and bodies having a thickness of l/s inch or less have been successfully used.

Although in the normal or uncompressed condition of the switch both contact parts 18 of each staple are out of contact'with the adjacent sheet, it will be understood that the circuit'through a particular staple will be open soV long as at least one of lits Contact parts is out ofV contact with the adjacent sheet. This permits a slight variation of construction, as is best illustrated in Figure 4, lin which the compressible pad b is provided with conducting sheets such for example as foraminous materiali 52 and 54 at opposite sides thereof. In this case how'- eyer, fastening elements such for example as `the staples 576er the rivets 58 extend through one of the conducting sheets, andl in theillustrated embodiment of the invention through the lower sheet S4. The fastening eiements coinpress the materialVA or, the conripixzssibleV pad as indicated atV 69` so that the upperportion of the fastening element is substantially spacedfrom the uppermost sheet ofcon- ,ducting material 52, Obviously,' when pressure -is applied overthe fastening elements, the adjacent portions of the Pfad. 50 are compressedandpermit 'the upper 'contact rsheet 52 to, engage the conductingfastening elements 5d or 5,3. Obviously, if preferred, thelfasteningclements could extend through the upper conducting sheet andpad and would leave the lower portions thereof normally spaced frointhe lower conducting sheet 54, Also, it will be, obvious that with this construction instead of providingvk a continuous conducting sheet' atrone side of the pad, separate conductors could be applied thereto and directly engaged by the connector elements such as the staples5pv or the rivets 58.

As stated above, it isan object ofthe invention to providea vehiclewarning system in which my improved pressure-responsive switch is incorporated, "Referring now to Figure 3, there is illustrated a warning systemA circuit which is adapted to be associated with the horn or other signal device of a` Vehicle to energize the same whenever the vehicle is occupiedlby an unauthorized per#y son. As illustrated therein, the horn relay 28 is connected in series with the conventional automobile storage` battery Sil-and the horn button switch 32 by aV circuit generally indicated at V34.

Said hornrrelay is also, connected in series with the switch, v described in detail above, by a second circuit 36V.` Switchlll will desirably beplaced within the vehicleso that when a person normally occupies the vehicle, the opposite metal sheets 14of the switch are urged together under pressure lmaking,Contact with the contact parts 18 of the connector elements orstaplesto lclose switch., 1i?, thereby energizing `thehorn relay v23.v Preferably, the switch will be concealed in the frontseat ofv i the vehicle so as `to be closed by the `weightof a 'person occupying the seat.

Inv the" normal use. .of aA vehicle v by authorized person-` nel",y itfwillof coursey be desirableV to permanently.. open.v

thefpirc'uitl to ,the `horn ,relay through pressure-responsive switchlll, and tofthis end a manual'swit'ch 381is vprovided in series cifrcuitwith` the horn relay and switch 10.

Switch willfbe close d ,wl1en` the vehicleis unattended; so that unauthorized entryofthervehicleand resulting-v closing4 ot switch lllgfvilll result-in energizationof*theV 'Switch 38, will preferably be located in a concealed position within the vehicle such ias. in the .glove .comparteinsl.

lCircuits 34 and 36 may be grounded as .indicated :at 401 and 4&2-l l Oriepoi'the elds of greatest utility of the .present in-V vention 1s ur providing .switch structures assembledffinY the )fort-uy of mats responsive tothe .weight of an a'utomo ment for examplejwhich may be lockedto prevent tarnp-V 4 v the door. Alternatively, a similar construction may be provided for actuating gates, and a 'particular eld of utility in this connection is in self-service orunattended parking lots 'wherein the customer drives his car onto the mat which has the effect of opening and holding open the gate, either alone or in conjunction with a suitable coin control mechanism for controlling oper'- ation of the gate For this purpose the basic switch construction illustratedV in Figures l, 2 and 4 is associated with protective means to form a matas will now be described in conjunction with Figure 5. in thisl figure there is shown the body of compressible material at 62 having at opposite surfaces thereof conducting sheets 64 and 56 which may conveniently be formed of foraminous i'naterialx Fastening elements formed of conducting material are provided at spaced points throughout lthe area of the body, one of such fastening elements being shown at 68. in this iigure the fastening element is shown as of the type normally spacedfrom both the upper and lower conducting sheets, but may if preferred be applied in accordance with theA disclosure of Figure 4 so as to extend through either the upper' or lower sheet. The upper and lower sheets 641 and 6d are of course connected to suitable conductors similar to the conductors 22-and 24 shown in Figure 2, so that engagement between one or more of the fastening elements ed with both of the sheets 64 and 66 completes a circuit. In order to protect the switch construction so far described from destructive action byvehicle wheels and to distribute the wheel pressure Weight over a wider pressure area,v it is preferably provided withat least an upper protective sheet 70 of a relatively hard and stiff material. Excellent results have been obtained when, in thecase of auto-4 mobile wheels, the kupper protective sheet 70 is formed offplywood or a wood product formed of groundwood and plastic, suchfor examplepas is presently sold under the trade name Masonite. Alternatively, andy for use with wheeledlvehicles lighter than an automobile, such as grocerystore pushcarts and the like, the upper protec tive ysheet may be` formed ofvmetal such for example as aluminum' or steel, or of any suitable plastic material In Vthe preferred construction for use under automobiles, as illustrated in Figure 5, a lower sheet 72 is provided which is similar to the sheet itl and the edges ofthe sheets are spaced apart about the structure by a spacer 74 which mayfor example be formed of a hard incompressible material. Where the spacers 74 areiformed of hard in, compressible material, the upper protective sheet 70 is somewhat flexible s o that under the weight of a vehicle wheelit is moved downwardly to a suicient extent t0 insure proper Acontact between one or more of the fastening elements dwithboth of the screens or other conducting sheets 64 and 66.` Alternatively, the spacer stripsv 74 Imay be formed of a compressible material suchvfor example aslrubber, in which case vflexibility of the relatively hardiand stiliV protectingsheet 70 is not an essential-requirementt However, in the dimensions in which the protective sheet is normally required it is inherentlyl llexible` to a degree to permit operation of the switch. The Aoperation of the switch` does not depend alone upon theexibility of the protective cover sheet '79 but upon the1 compressibility andmresilience of the body of ma; terialv 62 'between the two conducting sheets 64 and66.

VInV order that the completemat illustrated in Figure 5 Y comprising the upper protective sheet 70, the lower sheet.

Referring,no vvto Figure -there isl shown another embodimentlof the present invention. In this casefthe switch assembly `comprises a mat structure designed pri marily for use in controlling door movement in markets or the like. The construction is designed to providea waterproof enclosure for the operating parts offthe mechanism. As seen at the left of the figure, the mat may comprise a rubber mat body 80 having at least one edge tapered as indicated at 82 and having a recess 84 extending upwardly thereinto from the bottom thereof. The recess 84 is adapted to be closed by a closure element 86 which may conveniently also be formed of rub- -ber and sealed to the mat body 80 as indicated at 88, so as to provide a water-tight enclosure. Located within the recess S4 is the switch device comprising the fiat body 90 of resilient compressible material such for example as rubber, having associated therewith a lower screen or other conducting sheet 92, an upper conducting screen or conducting sheet 94, the resilient compressible body 90 being provided with elements 96 extending therethrough and adapted to form contacts with either or both of the sheets 92 or 94. As illustrated, the elements 96 are shown as staples extending through the upper conducting sheet 94 and having downwardly exposed contact portions received in recesses or dimples beneath the lower surface of the resilient compressible body 90. It will be understood that these elements may be of the types fully described in the foregoing.

Located in the recess 84 directly above the sandwich comprising the upper and lower conducting sheets and the interposed compressible resilient body is a hard stiff plate 98 which may be formed of metal, plastic or other suitable material. Preferably, a similar plate 100 is provided at the bottom of the recess directly above the closure element 86, although the lower hard stii plate 100 may if desired be omitted. if the lower hard stiff plate 100 is provided, its edges are spaced from the edges of the upper plate 98 by a spacer 101 of suitable dielectric material.

It will be observed that pressure applied to the upper tread surface of the mat body 80 is transmitted down wardly producing compression of the resilient compressible body and causing the conductive layers 92 and 94 to approach, thereby bringing about contact between one or more of the elements 96 with both of the conducting sheets.

As indicated at the right of Figure 6, when a hard sti sheet such as shown at 102 is provided and is formed of conducting material, it will be unnecessary to employ the conducting sheet 94 since the sheet 102 will serve to distribute pressure and also act as a contact element of the switch. fn this case a screen may if desired, be provided at the bottom of the resilient compressible body 90 or such screen may be omitted if a lower metal sheet such as illustrated at 104 is provided.

This construction is particularly useful in exposed locations since it is waterproof. The mat body may be formed of a suitable hard wearing rubber capable of t withstanding substantial Wear over extended periods. The use of the upper hard stii plate not only improves the wearing properties of the mat assembly, but also improves the feel since it prevents substantial local depression by weights applied thereto. lt has the additional function of distributing the weight load over a substantial area so that under anticipated loads it is effective to close a number of contacts simultaneously.

It will be understood that the pressure-responsive switch has a wide variety of other possible uses. For eX- ample, the switch may be incorporated in a oor mat at the entrance of a house to ring a bell or buzzer or to turn on a light, or such a mat may be positioned at the entrance or exit of a store for opening and holding open the door, or for preventing it from being opened, in response to pressure upon the switch provided by the weight of a person standing upon it; or similarly, such a mat may be used to switch on a spotlight, or to illuminate and direct attention to a xed message of warning or of instructions, or to set oftr a burglar alarm,

or the like. Also, the switch may be incorporated in a soft pad of suitable shape and dimensions for attaching to the advancing edge of a sliding or descending door or gate, or to a vehicle or machine, for use as a trigger to stop the movement of the mechanism in response to pressure on the pad as by contact with a person or other object. Also, the switch may be located in a floor mat adjacent to an electrically operated tool, so that whenever the workman stands on the mat in working position the energizing circuit of the tool will automatically be closed through the switch to actuate the tool.

T he switch does not have to be at in form or rectangular in shape, as shown in the drawing, but may be of any form and shape-such as cylindrical or tubular or convex-and of any dimensions that may be necessary or convenient for the fulfillment of its intended pur pose.

Obviously, of course, a single mat may incorporate a plurality of electrically independent conducting sheets at one or both sides of the compressible body for connection into separate circuits.

The drawings and the foregoing specification constitute a description of the improved pressure switch in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. A pressure switch comprising a body of compressible resilient dielectric material, a metallic electrically conducting and compressing element extending completely through said body and having a contact portion on at least one side of said body arranged to compress and to displace the localized adjacent surface portion of said body inwardly so as to thereby position said contact portion beneath the general surface of said body, a conductor engaging the general surface of said body and normally spaced from said contact portion of said element but engageable therewith when pressure is applied to said conductor over said contact portion.

2. A switch as defined in claim l in which said body comprises a flat pad.

3. A switch as dened in claim l in which said conducting and compressing element comprises a staple.

4. A switch as defined in claim l in which said conducting and compressing element comprises a rivet.

5. A switch as defined in claim l in which a plurality of conducting and compressing elements are provided, and said conductor comprises a sheet extending across all of said elements.

6. A switch as defined in claim l in which a plurality of conducting and compressing elements are provided, and said conductor comprises a sheet of foraminous material extending across all of said elements.

7. A pressure switch comprising a pad of compressible resilient di-electric material, two electrically conducting members engaging opposite surfaces of said pad, an electrically conductive connector element extending through said pad between said members and having a contact portion at one side of said pad extending across a portion of the surface of said pad and disposed to form an indentation in the surface of said pad and to space said contact portion from the adjacent one of said members.

8. A switch as defined in claim 7 in which said conducting members are in the form of sheets.

9. A pressure switch comprising a pad of compressible resilient cli-electric material, two electrically conducting members engaging opposite surfaces of said pad, an electrically conductive connector element having a first portion connected to one of said members and a second portion at the opposite side of said pad from said rst portion engaging the surface of said pad and compressing the portion of the pad therebeneath to form an indenta tion in the surface of the pad and to space said second portion from the adjacent conducting member.

10, Aiswitchvas deiinedfincQ-inewhichi saidcon nectar-element is-afstaplerf 11'. A; switcljr` asxdened .in cla1iml-9-in which`- said'lcoriv nectgnelemen-tfis a rivet',

12; Afswitch as defined .in'clai'rx`1`9fin` which saidf-con-l ducting'members aremctalscreens.

13.. A: switch as Jdeued in claim` 9finV which'I said c011-A ducting members are metal, rscreens und" said zconnector element is a staple.

ducting members are metal screens-and said connector element is'a'r'ivetl 15; A pressure switch comprisingia pad of compressible resilient di-el'ectric material,v v-twoelectricallyf. conducting members .engaging-:oppcsite: surfaces-of 4saidipzfui, 2111;: electrically ccm'ductiye connector.' element extending completely through said pad and having contact portions at opposite sidesiof said pad-spacedfapart a distance sub stantially: less than thief-uncompressed 1 thickness of saidVV pad to formk indentatons. iuopposite surfaces v of said? pad and to space said contact portions'-inwardly=from saidl conducting mexznbersfA 16J swifchnas denediu clim'f 15 linfwhch sadton :rector element is' a staple.

17.1 A-l switch: as-deined in claim' 15 in which* said-*f connector element is arivetzi Vconducting members areQmetal screcnst 19;"A- switchl'asi-dened inclam 1S in whichsaidfconnectorlelemen'tis astaple.

20. A .switch as -dened iny claim connector .element is arrivet.

18 .in whichl saidr References vCit-ed inthe file of thisv patent UNIT ED lSTATESPfYlEP-V1`S\ 

